Closing module for an optical arrangement

ABSTRACT

Closing module for an optical arrangement, in particular for an objective for microlithography, comprising an optically active closing element having a first axis and a holding device that fixes the closing element at least in the direction of the first axis, the holding device being configured for radial clamping of the closing element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a closing module for an opticalarrangement. The invention can be used in connection with themicrolithography utilised in the manufacture of microelectroniccircuits. It therefore also concerns a lens barrel which is suitable, inparticular, for use in a microlithography device, and a microlithographydevice including such a lens barrel.

Lens barrels composed of a plurality of modules are used in a largenumber of optical applications, in particular in the field ofmicrolithography mentioned above. The individual modules include, as arule, one or more optical elements such as lenses, etc. The end of sucha lens barrel in the direction of its optical axis is generally formedby a closing module having an appropriate optical closing element. Sucha closing module may serve the purpose, among others, of sealing theinterior of the lens barrel from the environment.

In particular in the field of microlithography it is necessary toposition the optical elements used in the lens barrel, for example, thelenses, with the greatest possible spatial precision with respect to oneanother, in order to achieve appropriately high imaging quality. Thehigh demands for accuracy are not least a result of the constant need toincrease the resolution of the optical systems used in the manufactureof microelectronic circuits to drive forward the miniaturisation of themicroelectronic circuits to be manufactured.

With increased resolution there are increasing demands not only for thepositional accuracy of the optical elements used, but also for theaccuracy of the optical elements themselves. The latter must bemaintained as fully as possible in the installed state throughoutoperation. It is especially necessary to keep the optical element asfree of stress as possible during operation to avoid imaging errorscaused by deformation of the optical element. In addition, there is aneed in this context to achieve the most favourable possible dynamicbehaviour of the optical system used, with the highest possible resonantfrequencies.

2. Description of the Related Art

For the optical elements, i.e. the lenses, etc., inside the lens barrela number of measures for achieving a mounting as stress-free as possibleare known. For example, a comparatively complex and expensive mountingfor such a lens inside the lens barrel is known from US patentapplication 2002/1063741 A1. Patent DE 101 39 805 C1 and patentapplication EP 1 094 348 A2 also disclose variants for the mounting oflenses inside the lens barrel.

However, the above-mentioned closing elements present a problem in thiscontext. They are in general mounted in a sealed manner in acorresponding mount, together with which they form the closing module.The closing elements, which are often plane-parallel plates, are oftenadhesively bonded to the mount. This type of fixing has thedisadvantage, firstly, that it is not free of stress, so thatdeformations of the closing element which impair the imaging quality ofthe system can occur. Secondly—even with closing elements originallymounted in an almost stress-free manner—such undesired deformation canoccur as a result of the unavoidable thermal expansion of the system inoperation. Finally, subsequent adjustment of the closing element is, inparticular, extremely difficult.

It is therefore the object of the present invention to make available aclosing module of the type mentioned initially which does not have theabove-mentioned disadvantages or at least has them to a lesser degree,and, in particular, makes possible a reliable mounting of the closingelement which is precise and free of stress in operation.

BRIEF SUMMARY OF THE INVENTION

This object is achieved by the present invention with a closing modulehaving the features of claim 1.

The present invention is based, firstly, on recognition of the fact thata reliable mounting of the closing element which is precise and free ofstress in operation is obtained if the holding device for the closingelement is configured to clamp the closing element radially. With radialclamping it is possible, in particular, to achieve a contact geometrybetween the closing element and the holding device which ensuresextensive decoupling of deformations between the holding device and theclosing element. Deformations of the holding device are thereforetransmitted to the closing element, if at all, to only a minimisedextent.

A further advantage of the radial clamping is simpler assembly and thepossibility of adjusting the closing element at all times. Unlike thecase with the known closing modules having a fixedly inserted closingelement, it is thus possible to react to changed boundary conditionsquickly and simply at all times.

In addition, it has been shown that, even with such a radially clampedconnection, the undesired ingress of external media or foreign bodies,etc., into the interior of the lens barrel can be reliably and simplyprevented.

The present invention is also based on recognition of the fact that areliable mounting of the closing element that can subsequently beadjusted according to the requirements of the imaging system is obtainedif the holding device is designed for tilting of the first axis of theclosing element.

An object of the present invention is thus a closing module for anoptical arrangement, in particular for an objective formicrolithography, with an optically active closing element having afirst axis, and a holding device fixing the closing element at least inthe direction of the first axis. The holding device is in this caseconfigured for radial clamping of the closing element.

A further object of the present invention is a closing module for anoptical arrangement with an optically active closing element having afirst axis, and a holding device fixing the closing element at least inthe direction of the first axis, the holding element being configuredfor tilting of the first axis of the closing element.

A further object of the present invention is a closing element for aclosing module according to the invention and a holding device for aclosing module according to the invention.

A further object of the present invention is a lens barrel, inparticular a lens barrel for a microlithography device, having a closingmodule according to the invention.

A further object of the present invention, finally, is amicrolithography device for transferring a pattern formed on a mask ontoa substrate, said device having an optical projection system thatincludes a lens barrel according to the invention.

Further preferred embodiments of the invention are apparent from thedependent claims and from the following description of a preferredembodiment made with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective representation of a preferredembodiment of the closing module according to the invention;

FIG. 2 is a schematic partial section through the closing module fromFIG. 1 along the line II-II;

FIG. 3 is a schematic perspective representation of the first holdingdevice from FIG. 1;

FIG. 4 is a schematic perspective representation of a second holdingdevice from FIG. 1;

FIG. 5 is a schematic representation of a preferred embodiment of themicrolithography device according to the invention with a lens barrelaccording to the invention;

FIG. 6 is a schematic perspective representation of a further preferredembodiment of the closing module according to the invention;

FIG. 7 is a schematic partial section through the closing module fromFIG. 6 along the line VII-VII;

FIGS. 8A-8H are schematic partial sections through further preferredembodiments of the closing module according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 to 5 a preferred embodiment of a closingmodule 1 according to the invention for an objective formicrolithography is first described in the following.

FIG. 1 is a schematic perspective representation of the closing module 1having a holding device 2 according to the invention that holds aclosing element 3 according to the invention in the form of aplane-parallel closing plate with a first axis 3.1. The first axis, inthis case, is an axis of symmetry of the closing element 3 disposedperpendicularly on the centre plane of the closing element 3. The centreplane forms the principal plane of extension in which the flat closingelement 3 primarily extends. In the case of closing elements configuredin the manner of lenses the first axis corresponds, as a rule, to theoptical axis of the lens-like closing element.

The holding device comprises an inner frame 2.1 to which three evenlydistributed holding elements—a first holding element 2.2 and two secondholding elements 2.3—are fixed. These holding elements 2.2 and 2.3, assecond contact partners, are in each case in engagement in a contactpairing with the closing element 3 as the first contact partner. Theholding elements 2.2 and 2.3, with respect to the closing element 3,each exert a clamping force on the closing element 3 that is directedradially towards the first axis 3.1. In other words, the closing element3 is clamped radially by the holding elements 2.2 and 2.3.

It is self-evident that the clamping force is not necessarily the onlyforce that is exerted by the particular holding element on the closingelement. Rather, further forces acting in different directions may beexerted on the closing element by the respective holding element.

In the respective contact area between the holding elements 2.2 and 2.3,respectively, and the closing element 3 a projection 2.4 and 2.5,respectively, on the holding elements 2.2 and 2.3, respectively, engageas contact elements in a V-shaped groove 3.2 disposed around thecircumference of the closing element 3. In this case the projection 2.4and 2.5, respectively, on the holding elements 2.2 and 2.3,respectively, exert the clamping force directed radially towards thefirst axis on the closing element 3.

The groove 3.2, which has a rounded base, is formed symmetrically withrespect to the centre plane 3.3 of the closing element 3 representingthe neutral fibre of the closing element 3. Furthermore, the projections2.4 and 2.5, respectively, on the respective holding element 2.2 and2.3, respectively, are so configured and oriented that the resultingclamping force exerted in each case on the closing element 3 is disposedsubstantially in the centre plane 3.3 disposed perpendicularly to thefirst axis 3.1, and therefore in the neutral fibre.

A minimisation of the bending deformation of the closing element 3 bythe clamping forces is thereby achieved, which has a positive effect onthe imaging quality of an optical system equipped with a closing module1 of this kind. It is self-evident that the clamping force concerned maydeviate to a greater or lesser extent from the path of the neutralfibre. This is dependent substantially on the tilting of the first axis3.1 with respect to the geometrical axis of the holding device 2. Asexplained in more detail below, this tilting can be varied with thepresent closing module 1.

The V-shaped groove 3.2 has, in a section containing the first axis,rectilinear flanks 3.4 and 3.5. Only at the base is it rounded, asmentioned. In such a section the respective projection 2.4 and 2.5 hasan upper and lower radius of curvature 2.6 and 2.7, respectively. Thedistance between the flanks 3.4 and 3.5 in the direction of the firstaxis 3.1 and the distance between the radii of curvature 2.6 and 2.7 inthis direction are so adapted to one another that the projection 2.4 and2.5, respectively, contact the flanks 3.4 and 3.5 in their rectilinearportion.

In a section perpendicular to the first axis the V-shaped groove 3.2 hasa smaller radius of curvature than the associated projection 2.4 and2.5, respectively, in the same section. Two substantially point shapedcontact sites between the projections 2.4 and 2.5, respectively, and theflanks 3.4 and 3.5 of the groove 3.2 are thereby achieved. In the senseof the present invention, the phrase “substantially point shaped contactsite” should be understood to mean that, with ideally stiff contactpartners having ideal geometry, a point shaped contact would beproduced. In reality, of course, depending on the stiffness of thecontact partners and their deviation from the ideal geometry, a smallpoint-like contact area is produced.

However, it is self-evident that with other variants of the presentinvention other geometries of the contact sites can be provided. Forexample, linear and area shaped contact sites may also be provided.

Through the contact pairing with two substantially point shaped contactsites per holding element 2.2 and 2.3, respectively, a self-adjustingclamping pairing is produced. Differences of level between the holdingelements 2.2 and 2.3, for example, can thereby already be compensatedwithin the contact area between the holding element 2.2 and 2.3,respectively, and the closing element 3, without significant stressesbeing introduced into the closing element 3. High imaging quality canthereby be achieved without complex and expensive mounting of theholding elements 2.2 and 2.3, respectively.

The holding elements 2.2 and 2.3, respectively, hold the closing element3 both in a positive connection and in a frictional connection in thedirection of its first axis 3.1 and in the radial direction. Inaddition, they also hold the closing element 3 in a frictionalconnection in its circumferential direction. This brings with it theadvantage that, by overcoming the friction, the closing element 3 can besimply rotated about its first axis 3.1, so that eventually, imagingerrors (form errors) of the optical system can be at least partiallycompensated.

In the present example a definitely determined mounting of the closingelement 3 with defined radial clamping forces is achieved by means of aconfiguration comprising two fixed mounts and one resilient mount. Thefirst holding element 2.2 forms the resilient mount while the two secondholding elements 2.3 each represent a fixed mount.

The plate-like second holding element 2.3, shown from its underside inFIG. 4, is fixed at each end 2.9 and 2.10 by means of screws 2.8 to anannular step 2.11 of the inner frame 2.1. The screws 2.8 pass withradial clearance through bores 2.12 and 2.13 in the second holdingelement 2.3.

The exact radial positioning of the second holding element 2.3 isensured by stops 2.14 on an annular shoulder 2.15 of the inner frame2.1. During assembly the second holding element 2.3 is pushed radiallyagainst the stops 2.14 before tightening of the screws 2.8, so that itsrear lateral faces 2.16 and 2.17 rest in each case against a stop 2.14.Recesses 2.18 in the shoulder 2.15 ensure that the holding element 2.3rests against the shoulder 2.15 only in the region of its ends 2.9 and2.10.

Since the plane of the second holding element 2.3, in the assembledstate, is aligned substantially perpendicularly to the first axis 3.1and substantially parallel to the clamping force exerted on the closingelement 3, in the assembled state, the second holding element 2.3 formsin the radial direction a substantially rigid fixed mount for theclosing element 3.

The first holding element 2.2, as a radially resilient mount is locatedopposite the two radial fixed mounts formed by the second holdingelements 2.3. The plate-like first holding element 2.2 shown in FIG. 3is also fixed at both ends 2.19 and 2.20 by means of screws 2.8 to theannular step 2.11 of the inner frame 2.1. Here, too, the screws 2.8 passwith radial clearance through bores 2.21 and 2.22 in the first holdingelement 2.2.

To achieve the radially resilient effect the first projection 2.4 of thefirst holding element 2.2 is arranged resiliently on a first holdingbody 2.23. The first projection 2.4 can be deflected resiliently in adirection which is at least approximately perpendicular to the firstaxis 3.1. In the direction of the first axis 3.1 the first holdingelement 2.3 is arranged substantially rigidly on the first holding body2.23. This is achieved by the central arrangement of the firstprojection 2.4 on a flexible beam 2.24 held at both ends. This flexiblebeam 2.24 is in turn formed by means of an elongated slot 2.25 in thefirst holding body 2.23 penetrating in the direction of the first axis3.1.

During assembly, which takes place after assembly of the second holdingelements 2.3, the first holding element 2.2—as a result of the radialclearance of the screws 2.8 in the bores 2.21 and 2.22—is displacedradially against the closing element 3 until it rests against theclosing element 3 with a defined radial pretension, i.e. with a definedradial clamping force. The pretension may be verified, for example, witha suitable gauge or the like. In this position the screws 2.8 are thentightened. The first holding element 2.2 thereby does not rest againstthe shoulder 2.5 of the inner frame 2.1.

Because of the resilient configuration of the first holding element 2.2,this pretension remains substantially constant even with thermalexpansion of the components in operation. In other words, through thisconfiguration, a decoupling of thermal deformations is achieved. Afurther advantage of this configuration lies in the compensation ofmanufacturing tolerances that is thereby achieved.

It is self-evident that, with other variants of the closing moduleaccording to the invention, it may also be provided that more than oneholding element is configured resiliently in this way. In particular,all the holding elements may be configured resiliently in this way. Itis also self-evident that the radially resilient configuration can beachieved in any other way. For example, the projection forming thecontact element with the closing element may, for example, be arrangedon a flexible beam which is held at one end instead of the flexible beamheld at both ends.

As is explained below, in particular with reference to FIGS. 2 and 4,the tilt of the first axis 3.1 of the closing element 3 with respect tothe geometrical axis 2.26 of the holding device 2 can be adjusted viathe two second holding elements 2.3. The geometrical axis 2.26 coincideswith the first axis 3.1 in the state represented in FIG. 1.

To be able to adjust the tilt of the first axis 3.1 of the closingelement 3 with respect to the geometrical axis 2.26 of the holdingdevice 2, the inner frame 2.1 and the respective second holding element2.3 are configured and arranged such that, in the assembled state, thesecond holding element 2.3 also represents a flexible beam held at bothends, the central portion 2.27 of the latter being freely deflectable inthe direction of the first axis 3.1 or of the geometrical axis 2.26,respectively.

Also arranged in this central portion 2.27 is the projection 2.5contacting the closing element 3, i.e. the contact element with theclosing element 3. Consequently, a deflection of the central portion2.27 in the direction of the first axis 3.1 or of the geometrical axis2.26, respectively, is transmitted to the closing element 3. Through thedeflection of the two projections 2.5 of the second holding elements 2.3spaced apart in the circumferential direction, therefore, it ispossible—within certain limits—to adjust the tilt of the first axis 3.1with respect to the geometrical axis 2.26 as desired. As this happens,the above-described contact geometry with two substantially point shapedcontact sites per contact pairing also ensures that, at most,comparatively small stresses are induced in the closing element 3.

To deflect the central portion 2.27 in the direction of the first axis3.1 or of the geometrical axis 2.26, respectively, a positioning element2.29 arranged in the region of the projection 2.11 on the inner frame2.1 cooperates with a contact face 2.28 in the central portion 2.27 ofthe second holding element 2.3. In the present case, the positioningelement 2.29 is a passive positioning element in the form of anadjusting screw 2.29 which is screwed into the inner frame 2.1. It isself-evident, however, that, in other variants of the invention, activepositioning elements such as piezo actuators, etc., may also beprovided. With such active positioning elements a regular and optionallyeven continuous adjustment of the tilting can be achieved by means of asuitable control system.

To make possible or facilitate, respectively, the defined deflection ofthe central portion 2.27, the respective second holding element 2.3 hasbetween its end portions 2.9 and 2.10 and the central portion 2.27 twoflexible portions 2.30 and 2.31 having a cross-section reduced in adefined manner. When the central portion 2.27 is deflected in thedirection of the first axis 3.1 or of the geometrical axis 2.26,respectively, the flexible portions 2.30 and 2.31 then undergo a defineddeformation.

Through the above-described configuration with the two axiallyadjustable fixed mounts in the form of the second holding elements 2.3and the non-axially adjustable, resilient mount in the form of the firstholding element 2.2, tilting of the first axis 3.1 can be adjusted, asmentioned. It is, however, self-evident that, with other variants of thepresent invention, complete axial adjustment of the closing element 3 inthe direction of its first axis can be provided. In other words, all theholding elements may be configured to be axially deflectable in acorresponding manner.

As can be seen, in particular, in FIG. 2, an annular gap 4 having asubstantially constant radial dimension in the circumferential directionis formed between the inner frame 2.1 and the closing element 3. Toprevent ingress of external media or foreign bodies through this gap 4into the interior of an optical arrangement having the closing module 1,the holding device 2 includes a purging passage 2.32. A purging mediumcan be conducted into the interior of the closing module 1 via thispurging passage 2.32. The purging medium then escapes from the interiorof the closing module 1 via the gap 4, thus preventing the ingress ofundesired substances into the interior of the optical arrangement viathe gap 4.

The gap 4 may have comparatively small dimensions so that even smallvolume flows of the purging medium suffice to produce this effect. Inparticular with so-called immersion applications in which the opticalarrangement is immersed in a liquid, i.e. the closing element issurrounded on its outer side by a liquid medium, the building up andmaintaining of a suitable static pressure can suffice to produce thiseffect. A continuous escape of the purging medium through the gap 4 isnot essential in this case.

As can be seen, in particular, in FIG. 1, the holding device 2 also hasan annular outer flange 2.33 spaced radially from the inner frame 2.1.This outer flange 2.33 serves as a connection to the adjacent componentsof an optical arrangement to which the closing module 1 is attached. Forthis purpose the outer flange 2.33 has three connecting areas 2.34 withthrough-bores for fixing screws or the like distributed evenly aroundits circumference. In addition, spacers 2.35, by means of which theaxial distance from the adjacent components can be adjusted, may beprovided in the region of the through-bores. Because of suitableclearance of the fixing screws in the through-bores, the whole closingmodule 1 can be adjusted with respect to the adjacent componentstransversely to the first axis 3.1.

The inner frame 2.1 is connected to the outer flange 2.33 via acircumferential wall 2.36 in the form of an envelope of a cone. Beforeand after each connecting area 2.34 in the circumferential direction,radial slots 2.37 and 2.38 extend through the outer flange 2.33 into thewall 2.36. The radial slots 2.37 and 2.38 are continuous in thedirection of the first axis so that tabs 2.39 resilient in the directionof the first axis are formed. The resilient tabs 2.39 ensure decouplingof thermal deformations between the closing module and the adjacentcomponents. They extend so far in the direction of the inner frame thata given predefined minimal stiffness of the holding device 2 is stillretained.

In the present example the material of the components of the holdingdevice 2 is adapted with respect to its coefficient of thermal expansionto the material of the closing element 3. In other words, the componentsof the holding device 2 are made of a material which has the samecoefficient of thermal expansion as the closing element 3. For example,if the closing element 3 is made of quartz, the components of theholding device 2 are made of invar, Zerodur or ceramic materials. If theclosing element 3 is made of calcium fluoride, the components of theholding device 2 are preferably made of a suitable special steel.

As a result, thermally-induced differential expansion does not occur.The radial spring effect of the first holding element 2.2 serves only togenerate the clamping force, which is substantially invariable inoperation. The clamping force exerted on the closing element 3 cantherefore be restricted within close limits to the required amountthroughout operation. This has a positive effect on deformation of theclosing element 3. The closing element 3 is then retained to thegreatest possible extent in a positive manner in all spatial directions.

However, it is self-evident that, in other variants of the invention,only a partial adaptation of individual components of the holding devicewith respect to the coefficient of thermal expansion may be provided,eventually.

FIG. 5 is a schematic representation of a preferred embodiment of themicrolithography device 5 according to the invention. Themicrolithography device 5 includes an optical projection system 6 withan illumination system 7, a mask 8 and a lens barrel 9 with an opticalobjective axis 9.1. The illumination system 7 illuminates a mask 8.Located on the mask 8 is a pattern which is projected via the lensbarrel 9 onto a substrate 10, for example, a wafer.

The lens barrel 9 includes a series of optical modules 9.2 havingoptical elements such as lenses or the like. At its end facing towardsthe substrate the lens barrel 9 is closed by the closing module 1 ofFIG. 1. The closing module 1 is connected to a purging device 11 whichconducts a purging medium into the interior of the closing module 1 viathe purging passage 2.32.

FIGS. 6 and 7 show schematic representations of a further preferredembodiment of the closing module 1′ according to the invention. Thisembodiment, in its basic construction, does not differ from that ofFIGS. 1 and 4 so that only the differences are discussed primarily here.

The difference from the embodiment of FIGS. 1 to 4 lies in the reversalof the contact geometry between the holding elements 2.2′ and 2.3′ ofthe holding device 2′ and the closing element 3′. Thus, in this case acontact element 2.4′ and 2.5′, respectively, having a V-shaped groove2.40′ on the respective holding element 2.2′ and 2.3′ forms the contactpartner with the circumferential edge of the plane-parallel closingelement 3′, which engages in each case in the groove 2.40′.

Here, too, however, it is ensured by appropriate adaptation of the radiiof curvature of the contact partners that two substantially point shapedcontact sites with the above described advantages of low stress in themounting are present between the respective holding element 2.2′ and2.3′ and the closing element 3′ in the region of each contact pairing.

Furthermore, through a configuration having the first holding element2.2′ as the radially resilient mount and two second holding elements2.3′ as the fixed mounts, the above-described definitely determinedmounting of the closing element 3′ is ensured here also. As in theembodiment of FIGS. 1 to 4, the radially resilient configuration of thefirst holding element 2.2′ is realised by the arrangement of the contactelement 2.4′ on a flexible beam that flexes perpendicularly to the firstaxis 3.1′ and is held at both ends. This flexible beam is again formedby means of a slot 2.25′ in the holding body 2.23′ penetrating in thedirection of the first axis 3.1′.

A further difference from the embodiment of FIGS. 1 to 4 is that all theholding elements 2.2′ and 2.3′ are fixed to the inner frame 2.1′ of theholding device 2′ via an active positioning element 2.29′. The activepositioning element 2.29′ displaces the respective holding element 2.2′,2.3′ in the direction of the first axis 3.1′. By means of thesepositioning elements 2.29′, therefore, not only the tilting of the firstaxis 3.1′, but also the axial distance of the closing element 3′ from anadjacent optical component, can be adjusted. The dimension of thecircumferential gap 4′ which is formed between the closing element 3′and the annular step 2.41′ on the inner frame 2.1′ can also be adjustedthereby.

FIGS. 8A to 8H are schematic partial sections through further preferredembodiments of the closing module according to the invention. They showby means of schematic partial sections different possible forms for thecontact pairing between the closing element 3″ and the respectiveholding element 2.2″.

The contact pairings of FIGS. 8A to 8C are similar to the contactpairing that can be used with the closing element 3 of FIGS. 1 to 4.These contact pairings having a groove in the closing element 3″ aresuitable in principle for use with closing elements 3″ of appropriatethickness. The contact pairings in FIGS. 8D to 8H are similar to thecontact pairing used with the closing element 3′ of FIGS. 6 and 7.Moreover, they are also especially suitable for thin closing elements3″. FIGS. 8C and 8F show special cases of the contact pairing with asingle contact site in each case.

It is self-evident in all cases that through suitable adaptation of thecurvatures of the contact faces a substantially line shaped contact sitecan be provided in place of a substantially point shaped contact site.Likewise, a contact site which is area shaped from the outset may alsobe provided. The contact sites of different types may also be combinedwith one another in any way within a pairing of contact faces.

The present invention has been described above with reference toexamples having three holding elements in each case. It is, however,self-evident that, in other variants of the present invention, adifferent number of holding elements may also be provided. Inparticular, more than three holding elements holding the closing elementmay also be provided.

Furthermore, the present invention has been described above withreference to examples having plane-parallel closing elements in eachcase. It is, however, self-evident that, in other variants of thepresent invention, a different geometry may be provided for the closingelement.

With the present invention a simple mounting of the closing element withlow stress is possible. Tight deformation tolerances of the closingelement within the range of a few nanometres can be maintained. The tiltof the first axis of the closing element relative to the geometricalaxis of the holding device, and the centering of the closing element,can be adjusted with high accuracy. The adjustments do not varythroughout operation. In particular with adaptation of the coefficientsof thermal expansion, sliding movements between the components, andtherefore so-called hysteresis effects in which such sliding movementsare not completely reversed, do not occur.

A further advantage lies in the avoidance of connections formed bymaterials, such as adhesive bonding or the like, through the use ofpurely frictional and positive-fit connections. This makes possible,firstly, simple assembly, disassembly, adjustment and readjustment.Secondly, the use of materials prone to contamination, such as plasticsor the like, is avoided. The closing module according to the inventionis therefore suitable for use with almost any wavelength.

A further advantage lies in the simple manufacture of the components ofthe closing module according to the invention. All the components can beproduced by simple manufacturing methods, such as turning, milling,erosion, etc.

1. A closing module for an optical arrangement, comprising: an opticallyactive closing element having a first axis; and a holding device thatclamps said closing element radially, and fixes said closing element ata point along said first axis. wherein said closing element and saidholding device participate in preventing an ingress of external mediainto an interior portion of said optical arrangement.
 2. The closingmodule according to claim 1, wherein the holding device is configured tohold the closing element by exerting clamping forces onto the closingelement which are disposed in a plane substantially perpendicular to thefirst axis, respectively.
 3. The closing module according to claim 1,wherein the holding device includes a number of holding elements assecond contact partners, which are in respective engagement with theclosing element as the first contact partner in a contact pairing, andexert, onto said closing element, a clamping force directedsubstantially towards the first axis.
 4. The closing module according toclaim 3, wherein a contact pairing having a groove arranged in acircumferential direction of the closing element and an associatedprojection engaging in the groove is formed in at least one contact areabetween the closing element as the first contact partner and a holdingelement as a second contact partner, the groove being formed on one ofthe contact partners and the projection on the other contact partner. 5.The closing module according to claim 4, wherein the groove is formed onthe closing element and the projection on the holding element.
 6. Theclosing module according to claim 3, wherein the first contact partnerand the second contact partner are configured such that a contactpairing having two substantially point shaped contact sites is produced.7. The closing module according to claim 3, wherein the contact pairingis configured such that the clamping force exerted by the holdingelement acts substantially in the neutral fibre of the closing element.8. The closing module according to claim 3, wherein at least one firstholding element is configured to generate the clamping force in themanner of a resilient mount.
 9. The closing module according to claim 8,wherein the first holding element comprises a contact element providedto cooperate with the closing element, and a holding body, the contactelement being arranged on the holding body to be resilient in adirection of the clamping force to be exerted on the closing element.10. The closing module according to claim 1, wherein the holding deviceis configured for tilting of the first axis of the closing element. 11.The closing module according to claim 1, wherein the closing element isa plane-parallel plate.
 12. The closing module according to claim 1,wherein the closing element has a principal plane of extension and thefirst axis is disposed substantially perpendicularly to the principalplane of extension.
 13. A microlithography device for transferring apattern formed on a mask onto a substrate, comprising an opticalprojection system that includes a lens barrel having a closing modulefor an optical arrangement, wherein said closing module includes: anoptically active closing element having a first axis; and a holdingdevice fixing the closing element at least in a direction of the firstaxis, wherein the holding device is configured to clamp the closingelement radially.
 14. A closing module for an optical arrangement,comprising: an optically active closing element having a first axis; anda holding device that tilts said closing element to orient said firstaxis, and fixes said closing element at a point along said first axis.15. The closing module according to claim 14, wherein the holding deviceincludes an inner frame and a number of holding elements connected tothe inner frame.
 16. The closing module according to claim 14, whereinthe closing element is a plane-parallel plate.
 17. The closing moduleaccording to claim 14, wherein the closing element has a principal planeof extension and the first axis is disposed substantiallyperpendicularly to the principal plane of extension.
 18. A lens barrelhaving a closing module according to claim
 14. 19. The lens barrelaccording to claim 18, wherein a gap is formed between the closingelement and the holding device and a purging device for directing apurging stream of a purging medium through the gap is provided.
 20. Theclosing module according to claim 14, wherein said closing element andsaid holding device participate in preventing an ingress of matter intoan interior portion of said optical arrangement.
 21. The closing moduleaccording to claim 14, wherein the components of the holding device areat least partially adapted to the closing element with regard to theircoefficients of thermal expansion.
 22. A closing module for an opticalarrangement, comprising: an optically active closing element having afirst axis; and a holding device that clamps said closing elementradially, and fixes said closing element at a point along said firstaxis.
 23. The closing module according to claim 22, wherein said closingelement and said holding device participate in preventing an ingress ofmatter into an interior portion of said optical arrangement.
 24. Theclosing module according to claim 22, wherein components of the holdingdevice are at least partially adapted to the closing element with regardto their coefficients of thermal expansion.
 25. A microlithographydevice for transferring a pattern formed on a mask onto a substrate,comprising an optical projection system that includes a lens barrelaccording to claim
 18. 26. A closing element for a closing moduleaccording to claim
 1. 27. A holding device for a closing moduleaccording to claim
 1. 28. A lens barrel having a closing moduleaccording to claim 1.